# Gne-Depletion in C2C12 Myoblasts Leads to Alterations in Glycosylation and Myopathogene Expression

## TL;DR

Reducing GNE in muscle cells changes glycosylation patterns and affects genes important for muscle function and energy metabolism.

## Contribution

This study reveals how GNE depletion alters glycosylation and downregulates key muscle-related genes in a C2C12 cell model.

## Key findings

- GNE depletion leads to changes in glycosaminoglycan expression and O-GlcNAcylation but not N-glycan remodeling.
- Muscle-specific genes like Scn4a, Cacna1s, Ryr1, and Pygm are downregulated in Gne knockout cells.
- Altered glycosylation may impair muscle signaling, excitability, and glucose metabolism.

## Abstract

GNE myopathy is a rare genetic neuromuscular disorder caused by mutations in the GNE gene. The respective gene product, UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE), is a bifunctional enzyme that initiates endogenous sialic acid biosynthesis. Sialic acids are important building blocks for the glycosylation machinery of cells and are typically found at the terminal ends of glycoprotein N- and O-glycans. The exact pathomechanism of GNE myopathy remains elusive, and a better understanding of the disease is urgently needed for the development of therapeutic strategies. The purpose of this study was to examine the effects of hyposialylation on glycan structures and subsequent downstream effects in the C2C12 Gne knockout cell model. No overall remodeling of N-glycans was observed in the absence of Gne, but differences in glycosaminoglycan expression and O-GlcNAcylation were detected. Expression analysis of myopathogenes revealed concomitant down-regulation of muscle-specific genes. Among the top candidates were the sodium channel protein type 4 subunit α (Scn4a), voltage-dependent L-type calcium channel subunit α-1s (Cacna1s), ryanodine receptor 1 (Ryr1), and glycogen phosphorylase (Pygm), which are associated with excitation-contraction coupling and energy metabolism. The results suggest that remodeling of the glycome could have detrimental effects on intracellular signaling, excitability of skeletal muscle tissue, and glucose metabolism.